title: Covalent and noncovalent intermediates of an NAD utilizing enzyme, human CD38.
abstract: Enzymatic utilization of nicotinamide adenine dinucleotide (NAD) has increasingly been shown to have fundamental roles in gene regulation, signal transduction, and protein modification. Many of the processes require the cleavage of the nicotinamide moiety from the substrate and the formation of a reactive intermediate. Using X-ray crystallography, we show that human CD38, an NAD-utilizing enzyme, is capable of catalyzing the cleavage reactions through both covalent and noncovalent intermediates, depending on the substrate used. The covalent intermediate is resistant to further attack by nucleophiles, resulting in mechanism-based enzyme inactivation. The noncovalent intermediate is stabilized mainly through H-bond interactions, but appears to remain reactive. Our structural results favor the proposal of a noncovalent intermediate during normal enzymatic utilization of NAD by human CD38 and provide structural insights into the design of covalent and noncovalent inhibitors targeting NAD-utilization pathways.
authors.affiliation: MacCHESS, Cornell High Energy Synchrotron Source, Department of Chemistry and Chemical Biology, School of Applied & Engineering Physics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Qun
authors.initials: Q
authors.lastname: Liu
authors.forename: Irina A
authors.initials: IA
authors.lastname: Kriksunov
authors.forename: Hong
authors.initials: H
authors.lastname: Jiang
authors.forename: Richard
authors.initials: R
authors.lastname: Graeff
authors.forename: Hening
authors.initials: H
authors.lastname: Lin
authors.forename: Hon Cheung
authors.initials: HC
authors.lastname: Lee
authors.forename: Quan
authors.initials: Q
authors.lastname: Hao
mesh_terms: D051997:ADP-ribosyl Cyclase 1 / Q000737:chemistry* / Q000378:metabolism*; D002384:Catalysis; D018360:Crystallography, X-Ray; D006027:Glycosides / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D015394:Molecular Structure; D009243:NAD / Q000378:metabolism*; D009537:Nicotinamide Mononucleotide / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding
chemical_list: D006027:Glycosides; D009243:NAD; D009537:Nicotinamide Mononucleotide; D051997:ADP-ribosyl Cyclase 1